Gas-solid fluidized beds are well known systems used in reactors and other practical applications such as particle drying and coating. Fluidized beds are formed when a mixture of solid particulate and fluid is placed under conditions which permit the solid/fluid mixture to behave with characteristics of a fluid. Typically, creating a fluidized bed comprises introducing pressurized fluid through the particulate medium. In some circumstances, so called fluidization of the solid/fluid mixture occurs where the pressure drop of the fluid across the particulate elements is sufficient to support the weight (minus buoyancy) of the particulate elements. Fluidized beds are used for a wide variety of industrial processes and/or applications, including, without limitation, fluidized bed reactors, fluidized catalytic cracking (FCC) reactors, fluidized bed combustion, heat or mass transfer applications and/or the like.
One fluidized bed application of considerable commercial importance is the FCC application, which is used, without limitation, in petroleum refineries. Typically, in such refineries, FCC processes are used to convert high-boiling, high-molecular weight hydrocarbon fractions of petroleum crude oils to more valuable gasoline, olefinic gases, and other products. In some typical FCC petroleum refining processes, the feedstock (fluid) used in the fluidized bed comprises a portion of crude oil (which may be referred to as heavy gas oil). The FCC petroleum refinery process typically comprises vaporizing and breaking (cracking) the long-chain molecules of the crude oil into shorter molecules by contacting the feedstock, at high temperature and moderate pressure, with powdered particulate catalyst in a fluidized bed.
There is a general desire to provide models which simulate the behavior of fluidized beds, such as, without limitation, those used in FCC processes and other industrial processes. Such models may, for example, provide a better understanding of reaction mechanisms taking place in the fluidized bed.
There have been prior art attempts to model or simulate the behavior of fluidized beds comprising gas/solid mixtures using computer-based simulation. So called “Computational Fluid Dynamics” (CFD) has been successfully used to model some aspects of the hydrodynamics of gas-solid fluidized beds. With its increased computational capabilities, CFD has become an important tool for understanding the complex phenomena between the gas phase and the particles in fluidized bed reactors. Prior art fluidized bed models can be classified generally as Eulerian-Eulerian, Eulerian-Lagrangian and Eulerian-Lagrangian Hybrid, based on the analytical framework used in the model. In general, the Lagrangian approach involves separate equations of motion for each particle in the flow field, whereas in the Eulerian approach, the solid and fluid phases are treated as separate interpenetrating continua, while the interactions between phases are accounted for by supplementary equations. So called Eulerian-Eulerian simulation may enable modeling of relatively large scale fluidized beds.
A challenge that is faced in CFD models for simulation of gas/solid mixtures in fluidized beds involves the different types of particulates and their corresponding properties. In particular, in Geldart, D. (1973), Types of Gas Fluidization, Powder Technology, 7(5), 285-292, Geldart proposed classifying particulate powders into so-called “Geldart Groups” A, B, C and D. Prior art CFD models for simulating the behavior of gas/solid mixtures in fluidized beds exhibit shortcomings when the particulates of interest comprises so-called Geldart group A particles. The most widely used catalyst particles in industrial FCC processes are Geldart group A particles. While the exact cause of the shortcomings of CFD models for Geldart group A is not well understood and without wishing to be bound by theory, some proponents have suggested that formation of agglomerates or clusters in and above a fluidized bed of FCC catalyst particles may be a major cause of inaccuracies in modeling and some suggest further that hydrodynamic factors may not be solely responsible for cluster formation, with cohesive forces, such as electrostatic, capillary and van der Waals forces, also playing a significant role.
There is a general desire to provide computer-implemented models which simulate the behavior of fluidized beds, such as, without limitation, those used in FCC processes and other industrial processes, where the particulate comprises Geldart group A particles.
There have been some prior art attempts to model fluidized beds with Geldart group A particles in the Eulerian-Eulerian framework with so-called “Sub-Grid-Scale” (SGS) models which attempt to model mesoscale structures including bubbles, clusters and agglomerates. These prior art attempts to provide SGS models in the Eulerian-Eulerian framework are reviewed in Wang, J. (2009), A Review of Eulerian Simulation of Geldart A Particles in Gas-Fluidized Beds, Industrial & Engineering Chemistry Research, 48(12), 5567-5577. These prior art fluidized bed models exhibit the drawbacks that they are generally limited to specific operating conditions and/or are dependent on arbitrary empirically-determined parameters, which limit their application to different fluidized bed systems and their corresponding industrial applicability.
There is a general desire to provide computer-implemented models which simulate the behavior of fluidized beds, such as, without limitation, those used in FCC processes and other industrial processes, where the particulate comprises Geldart group A particles, where the model improves upon, or at least ameliorates, the drawbacks associated with prior art fluidized bed models.
The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the description and a study of the drawings.